Land‐use change outweighs projected effects of changing rainfall on tree cover in sub‐Saharan Africa

Abstract

Global change will likely affect savanna and forest structure and distributions, with implications for diversity within both biomes. Few studies have examined the impacts of both expected precipitation and land use changes on vegetation structure in the future, despite their likely severity. Here, we modeled tree cover in sub-Saharan Africa, as a proxy for vegetation structure and land cover change, using climatic, edaphic, and anthropic data (R(2) = 0.97). Projected tree cover for the year 2070, simulated using scenarios that include climate and land use projections, generally decreased, both in forest and savanna, although the directionality of changes varied locally. The main driver of tree cover changes was land use change; the effects of precipitation change were minor by comparison. Interestingly, carbon emissions mitigation via increasing biofuels production resulted in decreases in tree cover, more severe than scenarios with more intense precipitation change, especially within savannas. Evaluation of tree cover change against protected area extent at the WWF Ecoregion scale suggested areas of high biodiversity and ecosystem services concern. Those forests most vulnerable to large decreases in tree cover were also highly protected, potentially buffering the effects of global change. Meanwhile, savannas, especially where they immediately bordered forests (e.g. West and Central Africa), were characterized by a dearth of protected areas, making them highly vulnerable. Savanna must become an explicit policy priority in the face of climate and land use change if conservation and livelihoods are to remain viable into the next century.

Multimodel Analysis of Future Land Use and Climate Change Impacts on Ecosystem Functioning

“…Several modeling studies have investigated the relative importance of historic or future LUC versus CC impacts on ecosystems by studying the effects on variables like vegetation cover and/or carbon cycling globally (e.g., Davies-Barnard et al, 2015;Devaraju et al, 2016;Levy et al, 2004;McGuire et al, 2001;Müller et al, 2007;Ostberg et al, 2015;Tharammal et al, 2018) or regionally (Aleman et al, 2016;Boit et al, 2016;Zaehle et al, 2007;Zhang et al, 2015). However, these studies were often restricted by the usage of only ©2019.…”

Tropical grassy biomes: linking ecology, human use and conservation

“…However, unlike other biomes, the contrasting life forms and physiologies of the dominant C 3 woody plant species and the grass species using the C 4 photosynthetic pathway sees the future of TGBs linked, in a profound way, to the ever-rising atmospheric CO 2 concentration and the global political agenda to reduce these emissions. Furthermore, TGBs have generally few policy and legislative mechanisms in place for their protection ( [11], see also the example provided by do Espírito Santo et al [12]). …”

Spatial patterns in the global distributions of savanna and forest

“…The mechanisms that determine biome distributions are a critical issue in modern ecology, especially in the context of predicting biosphere and carbon cycling responses to global change. Both climate and land‐use changes are expected to significantly impact the distributions of major biomes, especially in the tropics, where forest‐ and savanna‐type systems dominate (Aleman, Blarquez, & Staver, ; Higgins & Scheiter, ). In the tropics, climate change is leading to increasing temperature and, perhaps more importantly, to changing precipitation patterns (IPCC, ) and disturbance regimes (Malhi et al, ), which may affect both biome distribution and vegetation structure within biomes (Sala et al, ).…”

“…In the tropics, climate change is leading to increasing temperature and, perhaps more importantly, to changing precipitation patterns (IPCC, ) and disturbance regimes (Malhi et al, ), which may affect both biome distribution and vegetation structure within biomes (Sala et al, ). Direct anthropogenic impacts also constitute a direct threat to tropical ecosystems, via tropical forest loss and degradation (Aleman et al, ; Geist & Lambin, ) and losses of biodiversity in both forest and savanna biomes (Sala et al, ; Veldman, ).…”